Role of humoral presenitization in human renal transplant rejection

Bias in Medicine: Lessons Learned and Mitigation Strategies

Cognitive bias consists of systematic errors in thinking due to human processing limitations or inappropriate mental models. Cognitive bias occurs when intuitive thinking is used to reach conclusions about information rather than analytic (mindful) thinking. Scientific progress is delayed when bias influences the dissemination of new scientific knowledge, as it has with the role of human leucocyte antigen antibodies and antibody-mediated rejection in cardiac transplantation. Mitigating strategies can be successful but involve concerted action by investigators, peer reviewers, and editors to consider how we think as well as what we think.

C1q binding is not an independent risk factor for kidney allograft loss after an acute antibody-mediated rejection episode: a retrospective cohort study

After kidney transplantation, C4d is an incomplete marker of acute antibody-mediated rejection (AMR) and C1q-binding donor-specific antibodies (DSA) have been associated with allograft survival. However, the impact on allograft survival of C1q+ DSA after clinical AMR has not been studied yet. We analysed retrospectively in clinical AMR C4d staining and C1q-binding impact on allograft survival. We compared clinical, histological and serological features of C4d- and C4d+ AMR, C1q+ and C1q- DSA AMR and analysed C4d and C1q-binding impact on allograft survival. Among 500 for-cause kidney allograft biopsies, 48 fulfilled AMR criteria. C4d+ AMR [N = 18 (37.5%)] have significantly higher number class I DSA (P = 0.02), higher microvascular score (P = 0.02) and more transplant glomerulopathy (P = 0.04). C1q+ AMR [N = 20 (44%)] presented with significantly more class I and class II DSA (P = 0.005 and 0.04) and C4d+ staining (P = 0.01). Graft losses were significantly higher in the C4d+ group (P = 0.04) but similar in C1q groups. C4d+ but not C1q+ binding was an independent risk factor for graft loss [HR = 2.65; (1.11-6.34); P = 0.028]. In our cohort of clinical AMR, C4d+ staining but not C1q+ binding is an independent risk factor for graft loss. Allograft loss and patient survival were similar in C1q+ and C1q- AMR.

Allograft rejection and tubulointerstitial fibrosis in human kidney allografts: interrogation by urinary cell mRNA profiling

Because the kidney allograft has the potential to function as an in-vivo flow cytometer and facilitate the access of immune cells and kidney parenchymal cells in to the urinary space, we hypothesized that mRNA profiling of urinary cells offers a noninvasive means of assessing the kidney allograft status. We overcame the inherent challenges of urinary cell mRNA profiling by developing pre-amplification protocols to compensate for low RNA yield from urinary cells and by developing robust protocols for absolute quantification mRNAs using RT-PCR assays. Armed with these tools, we undertook first single-center studies urinary cell mRNA profiling and then embarked on the multicenter Clinical Trials in Organ Transplantation-04 study of kidney transplant recipients. We report here our discovery and validation of diagnostic and prognostic biomarkers of acute cellular rejection and of interstitial fibrosis and tubular atrophy (IF/TA). Our urinary cell mRNA profiling studies, in addition to demonstrating the feasibility of accurate diagnosis of acute cellular rejection and IF/TA in the kidney allograft, advance mechanistic and potentially targetable biomarkers. Interventional trials, guided by urinary cell mRNA profiles, may lead to personalized immunosuppression in recipients of kidney allografts.

Concurrent acute cellular rejection is an independent risk factor for renal allograft failure in patients with C4d-positive antibody-mediated rejection

BACKGROUND

Identification of risk factors for renal allograft failure after an episode of acute antibody-mediated rejection (AMR) may help the outcome of this difficult-to-treat complication.

METHODS

During December 2003 to February 2011, 833 kidney graft recipients underwent 1120 clinically indicated biopsies at our center. We reviewed the biopsy results and identified 87 biopsy specimens from 87 patients positive for the degradation product of complement component 4 (C4d) and acute AMR. We generated Kaplan-Meier survival curves and performed a multivariable analysis using the Cox proportional hazards regression model to identify risk factors for allograft failure after C4d+ acute AMR.

RESULTS

Among the 87 patients, 26 had a diagnosis of acute AMR according to the Banff '09 classification schema, 29 had acute AMR and chronic active AMR, 18 had acute AMR and acute T-cell mediated rejection (TCMR), and 14 had acute AMR, chronic active AMR, and acute TCMR. Kaplan-Meier survival estimates showed that concurrent acute TCMR (P=0.001, Mantel-Cox log-rank test), concurrent chronic active AMR (P=0.03), and time to biopsy (P=0.04) are associated with graft survival. The Cox proportional hazards regression analysis identified that concurrent acute TCMR (hazard ratio, 2.59 [95% confidence interval, 1.21-5.55]; P=0.01) and estimated glomerular filtration rate (hazard ratio, 0.65 [95% confidence interval, 0.48-0.88]; P=0.01) are independent risk factors for allograft loss. Concurrent chronic active AMR or time to biopsy was not associated with graft failure by the multivariable Cox analysis.

CONCLUSIONS

Our single-center study has elucidated that concurrent acute TCMR in kidney transplant recipients with C4d+ acute AMR is an independent risk factor for graft failure. Level of allograft function at the time of diagnosis was also an independent predictor of graft loss.

Pediatric renal transplantation in a highly sensitised child-8 years on

Highly sensitised children have markedly reduced chances of receiving a successful deceased donor renal transplant, increased risk of rejection, and decreased graft survival. There is limited experience with the long-term followup of children who have undergone desensitization. Following 2 failed transplants, our patient was highly sensitised. She had some immunological response to intravenous immunoglobulin (IVIg) but this was not sustained. We developed a protocol involving sequential therapies with rituximab, IVIg, and plasma exchange. Immunosuppressant therapy at transplantation consisted of basiliximab, tacrolimus, mycophenolate mofetil, and steroids. At the time of transplantation, historical crossmatch was ignored. Current CDC crossmatch was negative, but T and B cell flow crossmatch was positive, due to donor-specific HLA Class I antibodies. Further plasma exchange and immunoglobulin therapy were given pre- and postoperatively. Our patient received a deceased donor-kidney-bearing HLA antigens to which she originally had antibodies, which would have precluded transplant. The graft kidney continues to function well 8 years posttransplant.

The emerging role of rituximab in organ transplantation

Long-term acceptance of solid organ allografts remains a challenge. While many acute rejection episodes can be treated, new mechanisms of allograft damage are now being defined especially in kidney transplantation. Unexpected clusters of CD20(+) cells have been discovered in renal biopsies performed for clinical rejection. C4d deposition is now routinely seen in refractory rejection. Despite the rapid introduction of new immunosuppressive agents in transplantation, the search for an efficacious anti-B-cell agent remains. With novel mechanisms of allograft damage now being defined, it is important to consider how an anti-B-cell agent might fit into an immunosuppressive regimen. Rituximab is a high-affinity CD20 specific antibody that depletes the B-cell compartment by inducing cellular apoptosis. Thus, it is a rational choice for therapy in transplantation to abrogate B-cell mediated events. In this review, we will discuss the mechanisms of action of rituximab, and its use in for a variety of indications in solid organ transplantation. There are emerging case reports that show that rituximab may be an effective agent to treat antibody-mediated rejection, and post-transplant lymphoproliferative disorder. Rituximab has been frequently cited as an important adjunct therapy in desensitization protocols for highly sensitized transplant recipients as well as recipients of ABO incompatible transplants. Rituximab demonstrates promise in this regard and warrants additional consideration in prospective clinical trials.

Rituximab as treatment for refractory kidney transplant rejection

Recent studies have shown that a high density of CD 20+ cells are seen in patients who have steroid-resistant rejection episodes. Rituximab is a high-affinity CD-20 specific antibody that inhibits B-cell proliferation while inducing cellular apoptosis. Thus, it is a rational choice for therapy in transplantation to abrogate B-cell-mediated events. Twenty-seven patients were diagnosed with biopsy-confirmed rejection manifested by thrombotic microangiopathy and/or endothelialitis between 2/99 and 2/02 at our institution. These individuals were treated with a single dose of rituximab, in addition to other therapies, in an effort to reverse their rejection episodes. Twenty-four received additional steroids while 22 of the 27 patients were also treated with plasmapheresis and antithymocyte globulin (ATG). Only three patients experienced graft loss not associated with patient death during the follow-up period (605 +/- 335.3 days). In the 24 successfully treated patients, the serum creatinine at the time of initiating rituximab therapy was 5.6 +/- 1.0 mg/dL and decreased to 0.95 +/- 0.7 mg/dL at discharge. The addition of rituximab may improve outcomes in severe, steroid-resistant or antibody-mediated rejection episodes after kidney transplantation.

Beneficial effect of plasmapheresis and intravenous immunoglobulin on renal allograft survival of patients with acute humoral rejection

BACKGROUND

Acute humoral rejection (AHR) has been associated with enhanced graft loss. Our study compared the renal allograft survival of patients with AHR treated with plasmapheresis (PP) and intravenous immunoglobulin (IVIG) with allograft survival in patients with acute cellular rejection (ACR).

METHODS

We retrospectively analyzed all kidney transplants performed at our institution between January 1999 and August 2001 (n=286). Recipients were classified into three groups according to biopsy reports: AHR, ACR, or no rejection. The ACR group was further divided into early and late rejection (<90 and >90 days posttransplant, respectively).

RESULTS

After a mean follow-up of 569+/-19 days, the incidence of AHR was 5.6% (n=16). Recipient presensitization, delayed graft function, early rejection, and higher creatinine at diagnosis were characteristic of AHR. Most AHR patients (14/16) were treated with PP and IVIG. One patient received only IVIG, whereas another received only PP. All AHR patients were given steroid pulses, but only four received antilymphocyte therapy because of concomitant severe ACR. The ACR group comprised 43 patients (15%). One patient with mild rejection received no therapy, 20 improved with steroids alone, and 22 required additional antilymphocyte therapy. One-year graft survival by Kaplan Meier analysis was 81% and 84% in the AHR and ACR groups, respectively (P=NS). Outcomes remained similar when AHR patients were compared with those with early ACR.

CONCLUSIONS

We conclude that AHR, when diagnosed early and treated aggressively with PP and IVIG, carries a short-term prognosis that is similar to ACR.

Current status of immunological monitoring in the renal allograft recipient

With the appropriate combined use of different immune monitoring techniques, it is possible to derive sensitive diagnostic parameters for the transplant surgeon. However, the core biopsy or cytological examination of the graft continues to represent the gold standard for evaluating the specificity and sensitivity of these methods. With the development of newer monoclonal antibodies and a better understanding of the impact of immune processes on the behavior of various activation linked, T cell associated surface antigens, one may be able to secure further valuable information, with enhanced diagnostic and prognostic accuracy.

Transplantation immunobiology in relation to neural grafting: lessons learned from immunologic privilege in the eye

The principles of transplantation immunobiology are described and discussed in terms of their applicability to neural grafting, a newly emerging field dedicated to the ultimate goal of reconstituting central nervous system deficits with normally functioning tissue replacements. Unique anatomic and physiologic features of the eye, which are responsible for the phenomenon of immunologic privilege, are compared with the brain and considered in terms of their relationship to the principles of transplantation. The existence of immune privilege in the brain and the newly acquired understanding of immunologic privilege in the eye may offer strategies by which neural grafters can achieve significantly greater graft acceptance.